Microfluidic devices, broadly understood, and microreactors in particular, are typically devices arranged to take advantage of high surface to volume ratios available in channels or passages of multi-millimeter or sub-millimeter dimensions. Heat and mass transfer rates can become very large as process volumes shrink. Applications range from massively parallel biological screening utilizing very small amounts of reagent, laboratory reaction characterization and parallel catalyst screening to chemical production Particularly for microfluidic devices useful in chemical production applications, chemical durability, heat transfer capability, and pressure resistance or mechanical robustness become key attributes.